This invention relates to ball joints, and more particularly to ball joint assemblies having a retaining ring which permanently entraps and mounts a ball end portion of a ball stud in the socket of a body member.
There exist numerous proposals to provide for the retention of a swivel ball or ball head in a socket which will result in an assembly which provides increased socket housing and ball stud strengths while conforming to applicable industry standards, such as SAE standards. While many prior art devices conform to industry standards and present theoretically acceptable designs, tooling costs and assembly techniques make the resulting products commercially unacceptable.
Basically, all of the designs for a permanently assembled ball and socket arrangement are generally the same. A ball head member is received within a cylindrical or hemispherical socket, and is retained therein by some means such as either cold-forming the side wall of the socket over a portion of the ball head or retaining the ball head in the socket by a retaining ring which partially projects into a recess in the socket and partially projects into the socket wall. Commercially acceptable ball and socket arrangements are produced by machining a groove in the side wall of the socket which provides enough clearance in the side wall of the groove for a split retaining ring to be placed therein to accommodate for expansion of the ring for passage of the ball head therethrough. The groove is further machined to provide an oblique bearing wall for the ring to resist the withdrawal of the ball head and to act as a wedge when withdrawal forces are applied to the ball head. This arrangement has several disadvantages. One such disadvantage is the fact that the ring is permitted to ride axially with the ball head upon the application of a withdrawal force to a wedged position which is dependent upon the radii of curvature of the ball head and the cross section of the retaining ring, and upon the slope angle of the retaining wall with respect to the direction of the applied withdrawal force. A precise degree of play or movement of the ball head relative to the socket is required in many installations, and is difficult to determine in a ball and socket constructed in accordance with the above-described technique. Moreover, since sufficient clearance must be provided for the retaining ring to expand upon insertion of the ball head, considerable extra material must be removed from the socket wall. The removal of material from that wall, however, necessarily results in a weakening of the cross section of the socket, even assuming that additional areas of stress concentration are not created. An example of a ball and socket having a groove which is enlarged to accommodate for an expanding retaining ring may be found in U.S. Pat. No. 3,862,807.
Another example of a ball and socket joint having a retaining ring to securely hold a ball head against removal may be found in U.S. Pat. No. 3,787,128. In that patent, excess material is removed from the socket, since the hemispherical nature of the socket dictates that the socket extend no further than to the midpoint of the ball head, while the retaining ring must be located on the withdrawal side of the midpoint. One object of that patent is to provide an assembly in which there exists zero play because of wedging between a retaining ring, the ball and its socket, since the assembly is intended to serve as a swivel engagement between a swash-plate engaging shoe and a piston in a barrel-type hydraulic pump or motor. Tolerances in the assembly must be closely maintained since the insertion path of the retaining ring is wedge-shaped and the machining tolerances dictate the final zero play position of the retaining ring.
Other prior art is found in U.S. Pat. Nos. 2,856,250 and 4,435,101.